Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.38	11.311%	$141.788	$141.79	$141.80	$141.80
Purchase #2	$153.35	12.614%	$172.6936	$172.69	$172.70	$172.70
Purchase #3	$89.37	3.248%	$92.2727	$92.27	$92.25	$92.30
Purchase #4	$247.34	13.360%	$280.3846	$280.38	$280.40	$280.40
Purchase #5	$168.45	8.287%	$182.4095	$182.41	$182.40	$182.40
Purchase #6	$183.77	7.232%	$197.0602	$197.06	$197.05	$197.10
Purchase #7	$197.82	12.326%	$222.2033	$222.20	$222.20	$222.20
7 purchase totals =	$1,167.48		$1,288.8119	$1,288.80	$1,288.80	$1,288.90